The present invention relates to a wire-electrical discharge machining apparatus, and more particularly to a type thereof capable of performing an intricate three dimensional machining.
In a wire-electrical discharge machining, a workpiece is subjected to cutting by a suspended wire electrode. This is fundamentally two dimensional machining. Therefore, for a production of a final product having a complicated three dimensional shape as shown in FIGS. 3(a) and 3(b), a workpiece undergoes rotational indexing so as to angularly provide various machining faces to be machined.
According to a conventional electrical discharge machining apparatus in which a workpiece is movable in X and Y axes, an operator removes the workpiece upon completion of machining to a one machining face, and another machining face is provided for subsequent machining after positional adjustment relative to the wire electrode. Therefore, it would be almost impossible to perform unmanned or unattended machining. Further, due to regripping of the workpiece in order to change machining faces, minute positional error may be provided, and accordingly, it would be impossible to perform multi-polygonal machining with high dimensional accuracy. In order to overcome the above described deficiencies, another type of electrical discharge machining apparatus has been proposed as disclosed in Japanese Patent Application Kokai Nos. 56-45324, 58-10423 and Japanese Patent Publication No. 62-27935. This apparatus provides a rotation shaft, so called a B-axis shaft, which allows a workpiece to be rotated about its axis so as to eliminate removal and gripping of the workpiece relative to a chuck. Further, no particular attention is drawn to a supply of a machining liquid. Therefore, in this type of apparatus, flushing is applied in which the machining liquid flows at high velocity from a nozzle to remove lodged deposits at machining gaps.
However, if the intricate machining is required in order to obtain an intricate final shape, machining liquid does not sufficiently reach the machining gap only by the flushing. Flushing is available for two dimensional machining to a plate like workpiece, since the nozzle is easily accessible to upper and lower faces of the plate so as to sufficiently introduce the machining liquid into the machining gap. In case of the machining to polygonal faces with rotating the workpiece or with rotary indexing, however, various machining modes are conceivable such as machining to a stepped portion or to a hollow configuration as shown in FIGS. 4(a) and 4(b). In such cases, nozzles 5 and 6 cannot be positioned close to an internal machining gap 55 or 59. Accordingly, machining liquid may be scattered and the liquid is not sufficiently introduced into the machining gaps 55 and 59 only by the flushing. As a result, a wire electrode 2 may be cut.